PURPOSE: To form a master disk for focus plate having no 'roughness' and excellent diffusion characteristics.

CONSTITUTION: After a pattern is formed of photosensitive resin on a substrate 1, microlenses 2 are formed through a heat treatment. Then a conductive film 5 is formed on the substrate 1 and microlenses 2 and then a plating layer 6 is formed by plating. The plating layer 6 forms a clear border line between the microlenses 2 and the parts 3 in contact therewith, and the microlenses are made in contact with each other at an acute angle.